Work has been carried out on a number of structural problems related to proteins derived from the HIV-1 virus. Three dimensional solution structures of Nef and the N-terminal domain of HIV-1 integrase have been determined, and work on the ectodomain of SIV gp41 is underway. In addition the structure of a host factor, HMG-I/Y, complexed to DNA, that is executed for the formation of the preintegration complex has been solved.